The long term objectives of the proposed studies are to precisely define specific interactions between host cells and their secreted factors with the opportunistic bacterial pathogen, Pseudomonas aeruginosa (PA). Knowledge of these interactions and their sequelae will provide information critical to rational development of therapies to lessen or prevent the consequences of corneal inflammation which often lead to visual impairment. A single hypothesis will be tested: That appropriate regulation of immune cells, chemokines, and cytokines and an effective, controlled early host inflammatory (e.g., PMN) response determines whether or not PA keratitis is resolved and whether vision is restored or lost. Specific aims to test the above hypothesis are: Aim 1. To characterize the role of specific CXC and CC chemokines in the inflammatory response to PA ocular infection in genetically and aged susceptible vs. resistant inbred mice. Aim 2. To characterize the role of specific cytokines in the inflammatory response to PA ocular; infection in susceptible and resistant mouse models. Aim 3. To determine the role of specific cells [macrophages, PMNs, T cells, and Langerhans cells (LC)] in PA ocular infection in susceptible and resistant mouse models. To achieve these aims, molecular microbiological, immunological and biochemical methods will be used.